The ability to perform at the highest levels of swimming has been attributed to a number of factors including stroke mechanics, physical conditioning, and psychological factors. Therefore the key components of effective swim instruction and coaching programs include stroke mechanics instruction, training techniques designed to develop appropriate levels of physical conditioning, and the utilization of relevant assessment techniques for instructional diagnostics and feedback.
Stroke mechanics has only recently been supported by viable biomechanical theories and insights. Although previously propulsion was thought to be primarily related to the generation of drag forces or pushing against water, it is now believed that the fastest swimmers develop propulsive forces primarily derived from lift or Bernoulli effects. These forces are produced by the movement of the swimmers hand through the water in a lateral elliptical pattern. Two key elements in the completion of this pattern are hand angle relative to the direction of limb movement and the ability to accelerate the hand at appropriate positions throughout the range of this motion or swim stroke. In addition, the optimal stroke velocity may not necessarily be the maximal velocity that a swimmer is able to sustain. The utilization of the proper pull pattern is a function of neuromotor skill and limb strength. Given two swimmers with relatively equivalent pull patterns, the fastest swimmer will be the one who is able to generate the most power. However, to conclude that the strongest individual will be the fastest swimmer ignores the overwhelming importance of stroke pattern in determining swim velocity. In addition to the basics of hand angle and acceleration, a stroke pattern can be reduced to four components; outsweep, downsweep, insweep, and upsweep. Furthermore, strokes such as the backstroke and butterfly have other body components that are critical to proper technique including head and hip motion as well as multiple kick patterns.
Four measures of stroke mechanics known to be correlated with maximum swim velocity are stroke efficiency (distance per stroke), maximal stroke frequency, stroke balance, and stroke ripple. These four variables are inter-related, with power being an underlying influence of all four. In addition, the relationship of stroke propulsive efficiency to stroke velocity is influenced by the fact that drag increases to the cube of forward velocity, while forward velocity increases at a slower rate in proportion to stroke velocity. Elite swimmers take fewer strokes per pool length and yet maintain a stroke frequency equal to if not greater than lessor competitors. Balance of stroke reflects the contribution of each of the two arms. Stroke ripple provides an indication of the efficiency of power transfer to overall forward motion as well as the ability to moderate the effects of inertia. In addition to these basic measures of stroke mechanics, more advanced analysis is under development (Costill 1992). During the course of a stroke the time course profile of the various stroke components can provide valuable information for instruction and correction.
Both stroke efficiency and velocity are thought to be developed primarily through water based drills. Distance per stroke can be improved through emphasis of the elliptical pull pattern and hand entrance and hand exit exercises. Stroke frequency is improved by swim sprints at distances shorter than those of any of the competitive events. Sprint assisted exercise, the application of an assisting force, has been suggested as a means of improving both factors. Sprint-assist provides the opportunity to develop stroke velocity and efficiency at higher than maximum speed. A simple technique has been used by coaches to implement the sprint-assist technique via a line attached to the swimmer and the manual hauling of the line. Another method involves the use of a long bungi cord (surgical rubber cord) which is stretched the length of the pool. When the swimmer swims towards the anchor point, the cord contracts and applys an assistive force. Other systems, such as U.S. Pat. No. 3,861,675 which consists of a line, weights, and pulleys, can be used to apply a constant assistive force to a swimmer as well. An experimental system recently constructed at Stanford University employs a hydraulic motor and an overhead cable system which applys an assistive force to the swimmer. Similar methods have been utilized by track athletes. Runners have been pulled behind moving vehicles or have been trained to run on motorized treadmills at speeds above those which they are independently capable of achieving. These methods often result in improvements in stride length and stride frequencies. Floatation devices however, are the most prevalant training aid and are used to modify the bouyancy of the swimmer or of his limbs for the purpose of modifying movement and reducing the energy requirements necessary to sustain floatation. An example of this type of device is disclosed in U.S. Pat. No. 4,804,326.
Training to develop physical conditioning is an important component of swimming success. As is true for most athletic activities, natural ability has a strong influence as well. A high aerobic capacity appears to be a requirement for enhanced endurance in swimming as is the case for long distance running and cycling. A key contributor to strength is the cross- sectional area of primary limb muscles. Thus, it is not surprising to find that the ability to generate power is related to skeletal muscle mass. Several scientific reports exist suggesting a high correlation between competitive swim performance and the ability of the swimmer to produce power as measured by a dry land device. This relationship appears to be particularly true when swimming shorter distances, those accomplished in less than two or three minutes.
One of the key concepts of athletic training is specificity of training. To train for the marathon one must run long distances. To be competitive in cycling, one must cycle. Therefore, the training activity most appropriate to achieving optimal swimming performance is actual swimming. While a number of land based exercise devices have been developed as a means to improve the strength and or muscular endurance of the swimmer, their overall effectiveness has not been determined. Councilman states that high-resistance fast-speed protocols are important for competitive swimming, and are best accomplished by sprinting in the water. The consensus is that aquatic based activity is more appropriate in both the training and assessment of swimmers.
A second key concept of training is that of physiological "overload". An important element of physical adaptation to physical demands is that to achieve optimal results athletes need to train for various elements of the activity in excess of that faced when they compete. Thus in order to develop the strength needed to perform maximally it is argued that loads in excess of those encountered during the event must be experienced during the training phase. These training activities can be placed into four categories, isometrics, isotonics, isokinetics, and biokinetics.
Isometric exercise allows no external muscle shortening or rather changes in joint angle. While clearly improving strength, isometric exercises are of limited use in a dynamic sense and provide few benefits in terms of muscle recruitment patterns. Isotonic exercise utilizes a constant weight moved through a range of motion wherein skeletal muscle shortening and joint angle changes do take place. This is the most common form of "weight lifting" exercise. The criticism concerning this exercise mode is that once the weight attains inertia less effort is required to continue to lift the weight. Also, the limiting factor for lifting the weight is the strength of the weakest muscle required to move it through the entire range of motion. Isokinetic exercise devices use cams or elliptical arcs to overcome this problem. By moving the weights along predetermined arcs the effective weight changes as a function of mechanical advantage. The disadvantage of this exercise mode concerns limited acceleration throughout the range of motion and aforementioned problems with inertia. There has also been criticism of this exercise mode in terms of it's specialized nature and the lack of development of the stabilizers and antagonistic muscle groups.
Biokinetic exercise provides accommodating resistance and acceleration throughout the range of motion thereby obviating the problems of the previously described modes of exercise. Accommodating resistance refers to the fact that muscle fibers employed to move a limb through a range of motion can be numerous and varied. Because the strengths of these muscles differs, a device that can provide the appropriate maximal forces, regardless of the limb dynamics, promotes strength gains at all points throughout complex motions. In line with the complex nature of the ballistic movements associated with the activity of swimming, biokinetic devices will provide the most benefits as they most closely emulate appropriate athletic movements.
Many of the standard dry land exercise techniques are utilized to train swimmers. Isometric and isotonic exercises employed by swimmers are of the dry land variety. In addition to these, specialized dry land devices provide analogs of swimming motions and are classified as isokinetic and/or biokinetic. U.S. Pat. No. 3,731,921 reveals a bench for simulating and developing swimming movement. "The Swim Bench", model 26E from Fitness Systems of Independence Mo., attempts to duplicate the full range of stroke motion on dry land. This device employs a governor controlled frictional mechanism. Other such systems include the BioKinetic Swim Bench of BioKinetics Inc. and the Biokinetic Bench of Isokinetic Inc.. These latter two systems utilize an electromagnetic braking system. Dry land systems such as the various swim benches do not replicate the true stroke dynamics encountered while swimming the crawl nor do they duplicate the metabolic loads required during actual swimming exercise.
The application of resistive forces to the swimmer while swimming may be categorized into three classes. The first includes those techniques employing attachments to a free- swimming person and which utilize hydrodynamic frictional drag. The second category includes those that tether or connect the swimmer to a stationary portion of a pool or dry land. The third classification encompasses techniques which connect the swimmer to a device which permits full swimming motion over the distance of a pool length or lap while applying resistance to that forward motion.
Most swimming resistance devices fall into the first category. A commonly used technique involves the attachment of small tires or other readily available items to the feet or body of the swimmer. U.S. Pat. Nos. 3,517,930, 5,002,268, and 5,011,137 describe variable resistance swimmer training devices which provide various degrees of resistance by employing hydrodynamic drag appendages. In U.S. Pat. No. 4,302,007 Counsilman and Oprean describe a drag belt with drag pockets. In the second class, various ropes, bungi cords (surgical rubber cords), and other lines are employed to attach the swimmer to a stationary object. U.S. Pat. No. 3,988,020 is a swimming exercise and training apparatus which restrains a swimmer in both the forward and lateral directions. U.S. Pat. No. 4,524,711 provides for a tethering line which incorporates a limited amount of stretching. U.S. Pat. No. 4,529,192 alternatively restrains the swimmer with a pair of spring loaded shoulder pads.
The simplest variation of the third class is the use of bungi cords (surgical rubber cords) or lines by an assistant who follows the swimmer along the side of the pool or pays out the line while applying a degree of resistive force. Other more elaborate resistance systems attach to the swimmer via a line or rope and include weights and pulleys, and rotational frictional devices. U.S. Pat. No. 3,861,675 describes a swimmer training device consisting of a line, pulleys, and weights. U.S. Pat. No. 4,114,874 reveals a small, portable appliance which provides the swimmer with a resistive force via a line attached to a rotary frictional device, with a spring line recoil mechanism. The "Long Rope" (Fitness Systems model 65S) employed a mechanism similar to their Swim Bench, but permits the swimmer to exercise in the water. This device was said to provide improvements in stroke technique and resistance training. It was described as portable, isokinetic, variable speed, and possessing the ability to recoil 80 feet of rope. There are other exercise devices such as U.S. Pat. No. 4,934,694 which claim to be mechanically convertible to any sport, and therefore imply applicability to the sport of swimming. Specifics of such modifications are not revealed however, and no mention is made of modifications that would be necessary to the control system for use in swimming.
Assessment techniques require the measurement of various physical parameters during swimming and range from the trivial use of a stopwatch, to elaborate research installations. Measurement of speed is the primary variable of interest in competitive swimming, and is utilized by most swim instructors and coaches. One early device revealed in U.S. Pat. No. 2,825,224 described a spring-balance force scale for the purpose of indicating relative swimming stroke development, The swimmer swam tethered in a stationary position. Recently researchers have begun to investigate the contributions of various muscle groups to the swimming stroke mechanics (Bingham 1993) by employing techniques of electromyography. These investigations may lend insights into both stroke mechanics and muscle fatigue. Hull recently (Kelly 1993) developed a prototype system for the assessment of stroke mechanics in competitive swimmers. This system consists of a hydraulic motor, overhead pulleys and cable system that tows the swimmer through the water at high speeds. This permits the swimmer and coach to analyze differences in stroke at these speeds due to the lowered requirements of propulsion forces which are provided by the towing system rather than the swimmer. One technique for diagnostic measures of stroke mechanics is now commercially available. Bladimiro Mestre of Quebec, Canada, has developed four bio-feedback systems that analyze propulsive forces, resistances, stroke balance, and rhythms. These systems provide visual and auditory feedback based on measured swimming parameters.
The measurement of power production during swimming is one of the major goals of researchers in the field. Measurement of power in the arms has been used as a diagnostic in assessing swimming performance. Sharp (1982), demonstrated correlations between BioKinetic Swim Bench (BioKinetics Inc.) measures and times in the sprint free style. The direct measure of power produced while swimming would be useful, but is highly problematic due to the lack of adequate models of swimming hydrodynamics and bio- mechanics. Toussaint (1988) describes an elaborate system designed to measure power and drag forces during swimming. The method of U.S. Pat. No. 4,654,010 attempts to estimate relative power by the measurement of hydrodynamic pressures on the palm of the swimmers hand. This technique is problematic for theoretical reasons mentioned above.
A power related variable which has been commonly measured in the swimmer is termed excess force or excess power. By means of a tether, the velocity of the swimmer is controlled and the maximal force that can be generated by the swimmer at that set velocity is measured by use of a force transducer. Knowing the swimmer's displacement and the time interval, excess power can thereby be derived. This value, excess power, has been shown to be correlated to swim performance in shorter competitive swim events. A few researchers have developed systems for the measurement of excess force in laboratory. Costill (1986) assembled a computer based system for the measurement of excess force and power during front crawl swimming at one of several preselected speeds. This system utilized an electromagnetic braking system (The Biokinetic Bench of Isokinetic Inc.) adapted to accommodate a long line attached to the swimmer. The device of U.S. Pat. No. 4,082,267 describes the use of the simple voltage controlled generator means incorporated in the Bio-kinetic bench. A voltage signal representing speed and a force measurement derived from a load cell attached to a pulley on the line were supplied to a Personal Computer for recording and plotting. Klentrou (1991) utilizes an apparatus which measures force mechanically in conjunction with an electro-magnetic servo speed control system. This system is an adaptation of the CYBEX apparatus, U.S. Pat. No. 3,465,592. Ria (1990) employed a speed measurement system involving an overhead tethered pulley system. This was cumbersome, but provided an accurate instantaneous speed measure. For force measurement they employed a force transducer in a tethered swim configuration. These two values were multiplied to produce a measure termed "EMP" or External Mechanical Power. Another power measure that has been used for anaerobic power estimates by Rohrs (1991) involves the recording of maximal tethered force integrated over time. Recently, Fry (1991) incorporated aerobic and anaerobic power tests in a battery of tests designed to detect overtraining. Again it is clear that conducting such tests while swimming would be most appropriate for swimmers. The research systems and measures described above and others of generally similar capability are not commercially available.
Various physiological measures may also be used to estimate power production. The upper regions of the heart rate curve provide a somewhat linear indirect measure of the level of intensity of exercise from which relative estimates of swimming efficiency might be calculated. One technique of monitoring heart rate while swimming has been disclosed by U.S. Pat. No. 4,681,118. Dry-land systems such as U.S. Pat. No. 4,998,725 have also employed a direct feedback loop control of exercise resistance based on heart rate. Other physiological measures such as blood oxygen saturation, volumes of oxygen consumed and carbon dioxide expelled may be used as indirect measures of energy production or the metabolic intensity of exercise. Such indirect energy measures have typically been done only in controlled research experiments. Advanced research installations have recently employed swim flumes which permit the swimmer to remain stationary while the water flows around him. This permits researchers to attach various physiological monitoring devices to the swimmer.
It is quite apparent from the foregoing review and discussion that the application of current technologies for swimming instruction, training, and assessment is highly problematic. A review and critical analysis is now presented.
Advanced technology for the kinesthetic development of stroke mechanics during water based activities is not available. While a few commercial flotation, tethering and restraining systems claim to improve stroke mechanics, they provide only passive assistance under artificial conditions. Sprint-assist techniques employing a manual tow line or bungi cords are able to apply only uneven forces that vary over the course of a lap. Weight systems, such as U.S. Pat. No. 3,861,675 or the Power Rack provide constant forces, but only over limited distances, and at fixed force steps which are not practical for the precise individual adjustments which are necessary. The experimental systems such as the Stanford hydraulic towing device are cumbersome, can only be crudely adjusted for applied force, and are not commercially available. The commercial stroke mechanics assessment techniques which are available rely on auditory and visual bio-feedback. It is a well known principle that swimmers rely primarily on kinesthetic feedback ("the feel of the water"). This suggests that visual and auditory feedback are neither optimal nor appropriate for communicating with the swimmer. Any system that fails to provide kinethestic feedback to the swimmer circumvents the primary sensory system employed in the activity of swimming. Kinesthetic feedback-based stroke assessment systems are not commercially available.
Advanced biokinetic technology for training and physical conditioning while swimming is not available. Swimming-based training devices generally provide passive hydrodynamic drag resistance with little control. Mechanical friction devices or weight systems connected to a swimmer via a cable offer more resistance force, but are also passive and lack precise control. Although various dry land commercial devices claim to provide biokinetic exercise for swimmers, specificity of water movement and forces are difficult or impossible to replicate on dry land. Thus the dry land systems which simulate swimming motions are typically poor substitutes for water based drills. This has been supported in recent studies such as Roberts (1991) which failed to find any significant increase in benefit from dry land training that simulated swimming motions over other generic dry land training systems. Furthermore, generic exercise systems offer only restricted limb motions that inadequately provide for the complex muscle combinations encountered during swimming strokes.
Advanced technology for the quantified analysis and assessment of stroke mechanics is not commercially available, while commercial power analysis devices provide only passive measures of force and are incapable of active force measurement protocols. In addition, researchers developing power assessment protocols have had difficulty in adapting dry land biokinetic technology such as U.S. Pat. No. 4,082,267 (Costill 1992, page 179). Furthermore, the adaptation of such devices as the CYBEX provides only limited isokinetic control. Most stroke and power analysis research systems are extremely limited in scope, designed only to measure instantaneous speed and force. Finally, no single research system provides for the quantified analysis of a range of stroke mechanics measures such as stroke efficiency, balance, and ripple or the more advanced stroke component time course profile analysis.
It is also quite apparent from the foregoing review of prior art that no efforts have been made toward the development of a single device which would incorporate swimming instruction, training and assessment. Furthermore, no single device reviewed above incorporates any combination of instruction, training and assessment in further combination with advanced technology.
Many current research and commercial devices for swimming instruction, training and assessment require an assistant due to inadequate mechanical design, safety problems, or complex user interfaces. Clearly the requirement of an assistant limits the application of such devices in many circumstances.
Absent from the various devices and systems reviewed herein are control systems employing parametric biomechanical dynamic models or processing components. Biokinetic technology has relied primarily on the characteristics of analog control feedback loops. Such loops incorporate simple PID control algorithms and deal directly with a single sensor input and electric motor control variable such as voltage. Even devices incorporating microprocessor control provide only limited tragectory force/speed curves, and do not provide for modification of the feedback loop parameters. Other systems which incorporate physiological inputs, such as the aforementioned U.S. Pat. No. 4,998,725 employ a direct feedback loop control of exercise resistance. Such dry-land systems however are able to make simplifying assumptions due to the fact that power produced on a treadmill or cycle may be directly measured. The requirements of kinesthetic feedback and biokinetic motion systems include processing components which are able to dynamically adapt and respond to the complex loads and motions of swimming in real-time based on an indirect measure of activity. A biomechanic processing model accepts an ensemble of physiological and biomechanical inputs calculated from sensor signals and electrodynamic system variables, processes these input variables based on configurational parameters, and outputs a biomechanically based control signal which may then be converted into kinesthetic feedback or biokinetic motion.
Advanced control technology such as microprocessor based systems are not commercially available in swimming instruction, training and assessment devices. Current research systems for swimming instruction, training and assessment employ computers only in the data acquisition operations, and not for control functions. The adjustments of control parameters are performed manually. In addition to U.S. Pat. No. 4,934,694 and U.S. Pat. No. 4,998,725 described above, several generic dry-land exercise and training devices have been revealed recently, such as U.S. Pat. Nos. 4,778,175, 4,869,497, and 4,930,770, which incorporate microprocessors for improved exercise control precision. Other applications include U.S. Pat. No. 4,907,795 which utilizes a microprocessor for monitoring and storage of exercise activity measurements. Such systems however provide protocols of extremely limited complexity, and would not be adaptable to the requirements of swimming instruction, training and assessment. Furthermore, systems such as the aforementioned which employ microprocessors for control and/or monitoring do not provide for the capability of user programmed functions or protocols, but simply provide means for the programming of the parameters of fixed protocol programs. An additional limitation associated with various microprocessor controller systems that operate in conjunction with a personal computer systems is that the controller is either physically located within a personal computer, or is incapable of operating while disconnected from the computer.
In general, there is a lack of advanced technology in devices specific to swimming instruction, training, and assessment. Devices which provide for the techniques of sprint-assist and resistance training during swimming currently employ control and mechanical technology of limited sophistication and thus preclude accuracy and repeatability in their application. In particular, the application of forces to the swimmer during sprint-assist and resistance swimming must be accurately specified and controlled so that the resulting speed is close to the swimmer's natural speed. The greater the deviation from the natural speed, the greater the deviation in stroke mechanics. This requirement for fine percentage adjustment and control is particularly critical when dealing with young swimmers. Various dry-land controllers such as U.S. Pat. No. 4,778,175 rely on tables of values rather than to calculate control variables parametrically. This type of technique is inadequate where flexible complex algorithms are necessary. In order to implement appropriate biomechanical models as described above, advanced signal processing control technology would have to be employed. The requirements of real-time loop processing of complex control models and extensible programmable control models preclude the use of fixed analog or fixed logic control technologies.
Recently, advanced motor control technology such as that disclosed in U.S. Pat. No. 4,910,447 have improved the electric motor control capabilities of exercise devices. Such control methods however are inadequate for applications such as swimming instruction, training, and assessment devices. Swim training devices would require DC motor controllers which operate with very low voltages, over a wide range of currents and motor temperatures, and additionally provide dynamic braking. Furthermore, such devices must include reliable redundant overload and disabling circuits.
A further problematic area of current swimming technology is that of the user interface. For effective use, simple control panels are essential. Dry land exercise systems employing advanced technology often incorporate complex key pads and displays. Research systems, and in some cases generic exercise systems such as U.S. Pat. Nos. 4,869,497 and 4,934,694, employ personal computer systems to provide the user interface which include full alphanumeric keyboards and full page displays. Obviously it would be unfeasible for a swimmer to operate such systems from within a pool. The swimmer must be provided with a conceptually straightforward system that minimizes buttons and switches, as well as the quantity of displayed information.
The measurement of a swimmers physiological and biomechanical variables while swimming requires some form of telemetry. Various systems have been devised to transmit such variables as ECG and hydrodynamic pressure by way of radio telemetry. In consideration of the wide range of variables that may be required for swimming assessment, the problem of interference, available channels, channel bandwidth, and the simultaneous use of several physically adjacent devices, radio transmission becomes problematic. In addition, the size, shape, and location of a radio antenna must be considered as well. A more flexible and convenient system of transmission is clearly warranted.
Advanced technology for the statistical recording of quantified stroke mechanics and physical conditioning assessments for swimming is not commercially available. In addition, research systems providing such statistical summary information do so for only limited variables of interest.
Although various systems as mentioned above incorporate, or communicate directly or indirectly with personal computers, none fully utilizes the possibilities of such communication links. As discussed above, the major shortcoming of previous systems employing communication links is one wherein the personal computer is an integral component of the system. In other systems, the computer provides data collection and statistical functions. Given the complex functional, environmental, and logistic demands of swimming instruction and training in a team or institutional setting, considerable flexibility in the introduction of portable personal computers at pool side is warranted. The use of the external computer link should be complementary to the functions of a swimming device and optional. The data communications hardware interface employed should be generic, such as the RS-232 communications standard. In addition to the interchange of data and operational parameters, such an interface should provide for the downloading of protocol programs of machine language and provide as well for a remote over-ride and replication of the pool side swimming device user interface panel.
The swimming pool environment itself presents several engineering challenges. Electrical safety considerations in a pool area preclude the use of devices that employ AC mains as a power source. In addition, battery powered devices require specialized efficient power control circuitry and dynamic braking techniques, some or all of which are absent in the devices reviewed herein. Another consideration is that of the logistics of installation and physical size. In a crowded pool situation, often with two or more people per lane during practice sessions and a wide variety of starting platform sizes and installation techniques, pool deck space is limited. Many of the commercial or research devices mentioned previously are cumbersome or present a safety risk due to the amount of floor space required adjacent to the pool. Any device for use adjacent to the pool must provide for a convenient and rapid removal. In addition to the above mentioned concerns, installation is often problematic. Due to the nature of tiled decks around institutional pools, the surface is generally slick and permanent installations require the use of specialized mountings.
A major problem in the application of electromechanical technology in a swimming pool environment is the harsh corrosive halogenated atmosphere and pool water. Most devices possess an inherent limitation in their ability to resist such environments. Electromechanical systems susceptible to the corrosive environment may degrade slowly. Electronic systems however will often fail abruptly and completely in these atmospheres. Even if existing dry land systems could be adapted mechanically to swimming, they would be impractical from an economic viewpoint to maintain in such a corrosive environment. Researchers employing technology such as Biokinetic swim bench U.S. Pat. No. 4,082,267, the CYBEX device, and personal computers subject such devices to only relatively brief and periodic exposures to the pool environment. Manufacturers who have adapted dry land systems, such as the aforementioned "Long Rope" have found it necessary to eliminate electronic display devices from their pool side products due to corrosion, and encountered early failures of mechanical friction resistance technology due to water related failures. These and other failures have led to the withdrawal of products from the market. Another problem confronted by most devices is the rapid deterioration of nylon and other readily available synthetic ropes when exposed to pool water over long periods.
It is quite clear therefore that a system incorporating precise and rugged technology, for use by swimmers in a pool environment, that provided kinesthetic feedback for instruction, biokinetic training, and physiological and biomechanical performance assessment, as well as providing programmable measurement and control of complex relationships of speed, force, power, distance, and time, would offer a substantial contribution to the field of swimming.